Google Gson测试对象序列化/反序列化，以及自定义序列化实现

Love The Way You Lie 2023-02-13 14:53 8阅读 0赞

### Google Gson测试对象序列化/反序列化 ###

*   *  写在前面
     *  一、简单测试
     *   *  1.1、基本类型序列化与反序列化
     *  1.2、Object 示例
     *  1.3、数组 示例
     *  1.4、数组 示例
     *  1.5、泛型的序列化和反序列化
     *  1.6、混合类型 集合，如 \['hello',5,\{name:'GREETINGS',source:'guest'\}\]
     *  1.7、格式化
     *  二、Gson自定义序列化的实现
     *   *  2.1、先介绍一下，Gson本身实现的常见的几种序列化实现
         *  2.2、自定义 字段转换策略

## 写在前面 ##

## 一、简单测试 ##

### 1.1、基本类型序列化与反序列化 ###

@Test
        public void t1() { 
            // Serialization
            Gson gson = new Gson();
            System.out.println(gson.toJson(1));
            System.out.println(gson.toJson("abcd"));
            System.out.println(gson.toJson(new Long(10)));
            int[] values = { 1};
            System.out.println(gson.toJson(values));
    
            // Deserialization
            int o1 = gson.fromJson("1", int.class);
            Integer o2 = gson.fromJson("1", Integer.class);
            Long o3 = gson.fromJson("1", Long.class);
            Boolean o4 = gson.fromJson("false", Boolean.class);
            String o5 = gson.fromJson("\"abc\"", String.class);
            String[] anotherStr = gson.fromJson("[\"abc\"]", String[].class);
        }

*   *  1
     *  “abcd”
     *  10
     *  \[1\]

## 1.2、Object 示例 ##

/** * Object Example * {"value1":1,"value2":"abc"} */
    @Test
        public void t2() { 
            // Serialization
            BagOfPrimitives obj = new BagOfPrimitives();
            Gson gson = new Gson();
            String json = gson.toJson(obj);
            System.out.println(json);
    
            // Deserialization
            BagOfPrimitives obj2 = gson.fromJson(json, BagOfPrimitives.class);
            System.out.println(obj2.toString());
        }

需要注意： Gson可以很容易地序列化和反序列化静态嵌套类。  
但是，不能自动反序列化纯内部类，因为它们的无参数构造函数还需要一个对包含对象的引用，  
而在反序列化时这个引用是不可用的。可以通过使内部类为静态或为其提供自定义InstanceCreator来解决这个问题。这里有一个例子:

// public class InstanceCreatorForB implements InstanceCreator<NestedA.B> { 
    // private final A a;
    // public InstanceCreatorForB(A a) { 
    // this.a = a;
    // }
    // public A.B createInstance(Type type) { 
    // return a.new B();
    // }
    // }

## 1.3、数组 示例 ##

@Test
        public void t3() { 
            Gson gson = new Gson();
            int[] ints = { 1, 2, 3, 4, 5};
            String[] strings = { "abc", "def", "ghi"};
    
    // Serialization
            gson.toJson(ints);     // ==> [1,2,3,4,5]
            gson.toJson(strings);  // ==> ["abc", "def", "ghi"]
    
    // Deserialization
            int[] ints2 = gson.fromJson("[1,2,3,4,5]", int[].class);
    
        }

## 1.4、数组 示例 ##

@Test
        public void t4() { 
            Gson gson = new Gson();
            Collection<Integer> ints = Lists.newArrayList(1, 2, 3, 4, 5);
    
            // Serialization
            String json = gson.toJson(ints);  // ==> json is [1,2,3,4,5]
    
            // Deserialization
            Type collectionType = new TypeToken<Collection<Integer>>() { 
            }.getType();
            Collection<Integer> ints2 = gson.fromJson(json, collectionType);
        }

## 1.5、泛型的序列化和反序列化 ##

class Foo<T> { 
            T value;
        }
    
        class Bar { 
            String value;
        }
    
        @Test
        public void t5() { 
            Gson gson = new Gson();
            Foo<Bar> foo = new Foo<Bar>();
    
            // 错误示例
            String s = gson.toJson(foo);// 不是很正确
            gson.fromJson(s, foo.getClass()); // 失败
    
            // 以下是正确序列化/反序列化
            Type fooType = new TypeToken<Foo<Bar>>() { 
            }.getType();
            String s1 = gson.toJson(foo, fooType);
    
            gson.fromJson(s1, fooType);
    
        }

## 1.6、混合类型 集合，如 \[‘hello’,5,\{name:‘GREETINGS’,source:‘guest’\}\] ##

## 1.7、格式化 ##

/** * pretty style * <p> * { * "name": "GREETINGS", * "source": "guest" * } * { * "name": "GREETINGS" * } */
        @Test
        public void t7() { 
            Event event = new Event("GREETINGS", "guest");
            Event event2 = new Event("GREETINGS", null);
    
            Gson gson = new GsonBuilder().setPrettyPrinting().create();
            String jsonOutput = gson.toJson(event);
            String jsonOutput2 = gson.toJson(event2);
    
            System.out.println(jsonOutput);
            System.out.println(jsonOutput2);
        }
    
        /** * 空值 赋 null * {"name":"GREETINGS","source":null} */
        @Test
        public void t8() { 
            Event event2 = new Event("GREETINGS", null);
    
            Gson gson = new GsonBuilder().serializeNulls().create();
            String jsonOutput2 = gson.toJson(event2);
            System.out.println(jsonOutput2);
        }
    
        /** * 版本控制 * {"newField":"new","field":"old"} * <p> * {"newerField":"newer","newField":"new","field":"old"} */
        @Test
        public void t9() { 
    
            Gson gson = new GsonBuilder().setVersion(1.0).create();
    
            VersionedClass versionedObject = new VersionedClass();
    
            String jsonOutput = gson.toJson(versionedObject);
            System.out.println(jsonOutput);
            System.out.println();
    
            gson = new Gson();
            jsonOutput = gson.toJson(versionedObject);
            System.out.println(jsonOutput);
        }
    
        /** * 自定义命名 * {"custom_naming":"first","SomeOtherField":"second"} */
        @Test
        public void t10() { 
            SomeObject someObject = new SomeObject("first", "second");
            Gson gson = new GsonBuilder().setFieldNamingPolicy(FieldNamingPolicy.UPPER_CAMEL_CASE).create();
            String jsonRepresentation = gson.toJson(someObject);
            System.out.println(jsonRepresentation);
        }
    
        /** * 时间序列化 */
        @Test
        public void t11() { 
            Gson gson = new GsonBuilder().setDateFormat("yyyy-MM-dd'T'HH:mm:ssZ").create();
    
            String date = "\"2013-02-10T13:45:30+0100\"";
            Date test = gson.fromJson(date, Date.class);
            System.out.println("date:" + test);
        }

## 二、Gson自定义序列化的实现 ##

### 2.1、先介绍一下，Gson本身实现的常见的几种序列化实现 ###

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzQyMTA1NjI5_size_16_color_FFFFFF_t_70]

是的，Gson 本身只提供了这六种 ，关于驼峰式命名的转换，太有限了，先简单测试一下

*  POJO

@Data
    @AllArgsConstructor
    public class UserNaming { 
        String Name;
        String email_of_developer;
        boolean isDeveloper;
        int _ageOfDeveloper;
    }

*  IDENTITY

/** * 原序列 * FieldNamingPolicy.IDENTITY 测试 * {"Name":"Norman","email_of_developer":"norman@futurestud.io","isDeveloper":true,"_ageOfDeveloper":26} */
        @Test
        public void t13() { 
            GsonBuilder gsonBuilder = new GsonBuilder();
            gsonBuilder.setFieldNamingPolicy(FieldNamingPolicy.IDENTITY);
            Gson gson = gsonBuilder.create();
    
            UserNaming user = new UserNaming("Norman", "norman@futurestud.io", true, 26);
            String usersJson = gson.toJson(user);
    
            System.out.println(usersJson);
        }

*  LOWER\_CASE\_WITH\_UNDERSCORES
 *

/** * 下划线 * FieldNamingPolicy.LOWER_CASE_WITH_UNDERSCORES，测试 * {"name":"Norman","email_of_developer":"norman@futurestud.io","is_developer":true,"_age_of_developer":26} */
        @Test
        public void t14() { 
            GsonBuilder gsonBuilder = new GsonBuilder();
            gsonBuilder.setFieldNamingPolicy(FieldNamingPolicy.LOWER_CASE_WITH_UNDERSCORES);
            Gson gson = gsonBuilder.create();
    
            UserNaming user = new UserNaming("Norman", "norman@futurestud.io", true, 26);
            String usersJson = gson.toJson(user);
    
            System.out.println(usersJson);
        }

*  LOWER\_CASE\_WITH\_DASHES

/** * 驼峰中横线 * FieldNamingPolicy.LOWER_CASE_WITH_DASHES，测试 * {"name":"Norman","email_of_developer":"norman@futurestud.io","is-developer":true,"_age-of-developer":26} */
        @Test
        public void t15() { 
            GsonBuilder gsonBuilder = new GsonBuilder();
            gsonBuilder.setFieldNamingPolicy(FieldNamingPolicy.LOWER_CASE_WITH_DASHES);
            Gson gson = gsonBuilder.create();
    
            UserNaming user = new UserNaming("Norman", "norman@futurestud.io", true, 26);
            String usersJson = gson.toJson(user);
    
            System.out.println(usersJson);
        }

*  UPPER\_CAMEL\_CASE

/** * 驼峰首字母大写 * FieldNamingPolicy.UPPER_CAMEL_CASE，测试 * {"Name":"Norman","Email_of_developer":"norman@futurestud.io","IsDeveloper":true,"_AgeOfDeveloper":26} */
        @Test
        public void t16() { 
            GsonBuilder gsonBuilder = new GsonBuilder();
            gsonBuilder.setFieldNamingPolicy(FieldNamingPolicy.UPPER_CAMEL_CASE);
            Gson gson = gsonBuilder.create();
    
            UserNaming user = new UserNaming("Norman", "norman@futurestud.io", true, 26);
            String usersJson = gson.toJson(user);
    
            System.out.println(usersJson);
        }

### 2.2、自定义 字段转换策略 ###

*  UPPER\_CAMEL\_CASE

/** * 驼峰转空格 * FieldNamingPolicy.UPPER_CAMEL_CASE，测试 * {"Name":"Norman","Email_of_developer":"norman@futurestud.io","Is Developer":true,"_Age Of Developer":26} */
        @Test
        public void t17() { 
            GsonBuilder gsonBuilder = new GsonBuilder();
            gsonBuilder.setFieldNamingPolicy(FieldNamingPolicy.UPPER_CAMEL_CASE_WITH_SPACES);
            Gson gson = gsonBuilder.create();
    
            UserNaming user = new UserNaming("Norman", "norman@futurestud.io", true, 26);
            String usersJson = gson.toJson(user);
    
            System.out.println(usersJson);
        }

*  自定义 FieldNamingStrategy

/** * 自定义 - “”替换下划线 */
        @Test
        public void t18() { 
            FieldNamingStrategy customPolicy = new FieldNamingStrategy() { 
                @Override
                public String translateName(Field f) { 
                    return f.getName().replace("_", "");
                }
            };
    
            GsonBuilder gsonBuilder = new GsonBuilder();
            gsonBuilder.setFieldNamingStrategy(customPolicy);
            Gson gson = gsonBuilder.create();
    
            UserNaming user = new UserNaming("Norman", "norman@futurestud.io", true, 26);
            String usersJson = gson.toJson(user);
    
            System.out.println(usersJson);
        }

*  自定义2 FieldNamingStrategy

/** * 自定义字段 转换 * {"Name":"Norman","emailOfDeveloper":"norman@futurestud.io","isDeveloper":true,"Ageofdeveloper":26} */
        @Test
        public void t19() { 
            FieldNamingStrategy customPolicy = new FieldNamingStrategy() { 
                @Override
                public String translateName(Field f) { 
                    return StrUtil.toCamelCase(f.getName());
                }
            };
    
            GsonBuilder gsonBuilder = new GsonBuilder();
            gsonBuilder.setFieldNamingStrategy(customPolicy);
            Gson gson = gsonBuilder.create();
    
            UserNaming user = new UserNaming("Norman", "norman@futurestud.io", true, 26);
            String usersJson = gson.toJson(user);
    
            System.out.println(usersJson);
        }

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